1. Field of the Invention
The present invention relates to a camera having a zoom lens acting as a photographic lens. More particularly, the invention relates to a camera having a zoom lens driven by a motor for effecting a zooming operation. The invention also relates to a camera which detects photographic conditions such as a distance to a photographic object, and automatically effects a zooming operation in accordance with detected photographic conditions.
2. Description of the Prior Art
Conventional cameras include those which have what is known as a power zoom mechanism for effecting a zooming operation with motor drive. The cameras having the power zoom mechanism include a switch for designating a zooming direction. The photographer carries out zooming of the photographic lens by operating this switch. With the power zoom mechanism as noted above, the photographer tends to take photographs inadvertently at a high magnification side (long focus side). This often results in peripheral potions of a portrait or the like slipping out of a picture area, or a required background not shown within a picture area. Conversely, if a picture is taken at a low magnification side (shorter focal length), the photographer tends to pay attention only to an object in the center, with the consequence that the center object appears smaller in a finished photograph than was intended although the photographer believed that he or she took steps to obtain the center object in a large size. This is because the photographer failed to take into account photographic conditions such as a distance to the object, photographic magnification and the like.
Also known are cameras having what is known as an auto zoom mechanism for automatically zooming for a predetermined focal length corresponding to a distance to a photographic object. Generally, cameras having the auto zoom mechanism also include a power zoom mechanism, and hence a switch for selecting a zooming direction as well. With conventional cameras as noted above, the zoom lens is driven opposite to an auto zooming direction when the switch is operated for zooming opposite to the auto zooming direction during an auto zooming operation (i.e. while automatic zooming is effected for a focal length corresponding to a distance of an object). If the switch is released from the above state, the zooming direction will return to the auto zooming direction. Therefore, where the auto zoom mechanism is incorporated into a video camera or the like which photographs images continuously, and the above control operation is effected, the photographed images will have frequently changing field angles, which renders reproduced images difficult to switch.
Further, there is a known mechanism in which a focal length of a zoom lens is detected by an encoder pattern and a brush slidable thereon. However, the encoder pattern provides information only with a limited degree of precision, which makes it difficult to effect auto zoom control with high precision, for example.
Among the cameras having the power zoom mechanism and the autofocusing mechanism, there are those which, when a focusing lens is driven to an end of the shortest photographic distance during an autofocusing operation, automatically effects a zooming operation to the short focal length side accordingly (Japanese Patent Publication Kokai No. 60-143310). Zoom lenses of the inner focus type and rear focus type include those in which the shorter the focal length is, the smaller the focusing lens is extended with respect to objects at the same distance. The above cameras with this type of zoom lens have a function for enabling an autofocusing operation with respect to a nearby object as much as possible. With these cameras, however, since a zooming operation is effected only after the focusing lens is driven to the end of short photographic distance side, there occurs a time lag before an in-focus condition is attained in the short photographic distance side.